In general, a common rail engine is an engine that stores fuel in a common rail as a high-pressure fuel storage device and injects the fuel into a combustion chamber of a cylinder at high pressure more than a predetermined pressure to burn the fuel. In this case, the common rail engine always maintains a constant pressure irrespective of an injection cycle and separately performs pressure maintenance and injection of the fuel. For this reason, the pressure and injection time of the fuel can be controlled depending on the operation condition of the engine so that the amount of an exhaust gas discharged from a diesel engine can be reduced, the ride comfortableness of the equipment such as an excavator can be improved, and fuel efficiency can be increased.
In case of the above-described common rail engine, in the case where the work is completed and the equipment is suspended in operation so as to be left to stand idle by the start off of the engine, the remaining fuel remained after being combusted on the engine is returned to a fuel tank along a return line by a pressure difference and a fuel supply circulation cycle. In this case, a phenomenon occurs in which a plunger and a barrel are not completely sealed externally, and in which the fuel leaks to a valve cover through such a portion and air in the valve cover flows in inversely. In addition, in the case where the fuel is not remained in the engine, the start-up performance of the engine is degraded, so that an error signal is indicated on an instrument board of an operator cab or the operation of the equipment becomes impossible.
For this reason, since an operator is required to manually manipulate a hand pump (referring to a prime pump operated manually) for start-up to supply fuel to the engine, and manipulate the hand pump, whenever necessary, he or she suffers from a great inconvenience.
In addition, since a pressure is significantly increased due to the excessive manipulation of the hand pump and the hand pump is used as occasion demands, internal leakage of fuel and damage of the hand pump may be caused. Besides, there may occur a problem in that the check valve installed between the fuel tank and the hand pump is damaged.